Addressing Global Water Stress using Desalination and Atmospheric Water Harvesting: A Thermodynamic and Technoeconomic Perspective

Freshwater is a critical resource for many sectors of the economy, but excessive withdrawal of natural freshwater reserves has resulted in global water stress that is projected to impact 4 billion people by the end of this decade. Methods of artificially producing freshwater include desalination, which is a well-established technology in which water is extracted from a saline solution (typically seawater). Atmospheric water harvesting (AWH) is an alternate emerging approach in which water vapor is extracted from ambient air and condensed into freshwater. AWH has recently attracted attention for decentralized water production, but a comparative analysis of these different technologies using the same performance (kWh/m3) and cost metrics ($/m3) does not exist. Herein we develop the first thermodynamic and technoeconomic framework for clean water production that considers the population and water risk across all global locations. We find that AWH consumes more energy than practical desalination with subsequent water transport for roughly 90% of the global population, even when AWH operates under reversible (albeit impractical) operation. Furthermore, a practical AWH system is far more expensive (6× – 40× depending on the location and AWH technology used) than seawater desalination on a levelized cost of water (LCOW) basis, even after accounting for the costs associated with transporting desalinated water inland. The one exception is when water transport costs are increased by 5×, resulting in sorbent AWH becoming the lowest cost option for arid locations far from the coast (e.g., Sahara Desert). Our analysis framework informs cost and performance targets (material and system level design tradeoffs) for technology deployment that maximizes global impact.